With increasing consciousness of energy problems in recent years, there has been a demand for a power source or power supply having a higher energy density and involving clean emissions. Fuel cells are power generators having an energy density several times that of existing batteries, and are characterized in that they have a high energy efficiency, and give off no or few nitrogen oxides or sulfur oxides as contained in emission gases. Thus, the fuel cell is a very effective device which fulfills requirements for a next-generation power supply device.
The fuel cell, which obtains an electromotive force by an electrochemical reaction between hydrogen and oxygen, needs hydrogen as a fuel. A known example of equipment for producing a hydrogen gas is a hydrogen production apparatus of a structure having a reaction container accommodating a metal hydride (boron hydride salt), and a water tank, and adapted to jet water within the water tank at the metal hydride inside the reaction container by a pump (see, for example, Patent Document 1).
With the conventional hydrogen production apparatus, when hydrogen is produced by supplying water to the metal hydride, it is expected that the products build up or stay on the metal hydride to coat the metal hydride, lowering the rate of reaction. Thus, it has been practiced to dispose the metal hydride in an upper part of the container, and spray the bottom surface of the metal hydride with water, thereby dropping water, which has not been used in the reaction, and the products onto a bottom part of the container. Water which has not been used in the reaction is recovered into the water tank by the pump, but once accumulates at the bottom part of the container.
As noted above, the hydrogen production apparatus has been restricted in its attitude or orientation during usage such that the metal hydride is disposed in the upper part of the container, and water and the products are dropped onto the bottom part of the container. If the conventional hydrogen production apparatus is used in a changed attitude or orientation, the metal hydride is coated with the products. Since water remaining unused in the reaction does not drop onto the bottom part of the container, moreover, the problem occurs that the water cannot be recovered into the water tank. Furthermore, the water unused in the reaction contacts the metal hydride again, and the recontacting water causes a hydrogen reaction.
If water once accumulating at the bottom part of the container contacts the metal hydride because of the change in the attitude or orientation, in particular, unexpected hydrogen production occurs, posing the serious problem that it becomes impossible to control the reaction. As a result, it has been unrealistic to use the hydrogen production apparatus as a power supply device for portable instruments, such as a cellular phone and a digital camera, which require a structure adapting to an attitude change.    Patent Document 1: JP-A-2002-137903